Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1987 Mercedes Benz 300SDLFACTORY OEM SERVICE PROCEDURE
Airflow Sensor
- With engine off, disconnect airflow sensor connector. Airflow sensor is located on right front wheelhousing between air cleaner and turbocharger. Connect multimeter and set to ohm scale. Probe and check resistance between terminals No. 2 and 3 of airflow sensor.
- Resistance should be 50-200 ohms at idle and 560-1100 ohms at fully open position. If resistance is okay, go to next step. If resistance is not to specification, check airflow sensor plate for dirt and binding. If necessary, replace airflow sensor.
- With engine off and ignition on, set multimeter to volts scale. Check voltage at terminals No. 1 and 2 as well as terminals No. 2 and 4 on airflow sensor connector. Voltage reading should be 5 volts. If voltage reading is 5 volts, testing is complete. If voltage reading is not 5 volts, repair open circuit. If no open circuit is found, replace EDS control unit. See Fig 1 .
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.